The present invention relates to the field of seals used in the rolling bearings, and more particularly in the rolling bearings operating in an aggressive outdoor environment due to the presence of various kinds of pollution, such as splashing water, dust and other foreign matter, to the exposition of the ultraviolet radiation emitted by the sun, and to the variations of temperature.
This is notably the case of the rolling bearings used in a wind turbine in order to angularly orient the rotor of the turbine according to the direction of the wind.
Otherwise, in the case of rolling bearings, and more specifically in the case of large-sized rolling bearings used for instance in such wind turbine, each time the bearing is lubricated, there is a high increase in the pressure inside the bearing. During this operation, the pressure may raise to 0.4 MPa. Thus, there is a risk that the surplus grease will be ejected from the bearing at the location of the seals. In the case of large-sized rolling bearings, pressure relief valves arc provided to allow this surplus grease to be ejected. Nonetheless, the surplus grease does sometimes escape from the bearing via the seals rather than through these valves.
However, there are numerous applications in which an escape of grease through the bearing seals must be reliably avoided, both during the lubricating of the bearings, i.e. while the interior of the bearings is being pressurized, and during normal running of the bearings, even in the case of relative movements that the two rings may do in addition to the rotational movements, under the action of the loads on the bearing. Such relative movements of the rings are relatively important more especially as the rolling bearing has a large diameter.
With the aim of avoiding this drawback, document FR-A-2 778 954 discloses a sealing arrangement for a rolling bearing comprising at least one row of rolling elements between first and second rings which are concentric and radially separated from one another by an annular space. This arrangement comprises at least an elastic seal fixed to the first ring and exhibiting a lip pressing against a bearing surface situated on the second ring inside the annular space. The lip of the seal is shaped in such a way that the force with which it presses against the bearing surface increases with the pressure inside the bearing.
With such a sealing arrangement, the lip opposes effectively any escape of grease, not only during lubrication but also during normal running of the bearing.
However, the sealing arrangement disclosed in this document has the drawback of being force fitted into a groove formed on the inner ring of the rolling bearing in order to obtain its retaining on the ring. This is detrimental in terms of mounting time and of cost.